Hydrostatically powered messenger style wire cutter

ABSTRACT

A hydrostatically actuated messenger type wire cutter for severing wire below the surface of a body of water consisting of a slide having an assembly for actuating a cutting tool to sever or weaken the wire at a preselected depth. A rupture disk collapses at the preselected depth, permitting water pressure to react against a piston carrying the cutting edge.

United States Patent Burke HYDROSTATICALLY POWERED MESSENGER STYLE WIRE CUTTER John C. Burke, North Falmouth, Mass.

Assignee: The United States of America as represented by the United States Atomic Energy Commission Filed: Dec. 18, 1970 Appl. No.: 99,381

lnventor:

us. 01. 83/1, 83/639, 83/925 R,

v 1 14/221 A 1111. C1 ..B26d 5/12 Field ofSearch ..83/l 639, 925 R; 114/221 A 1 51 May 16, 1972 [56] References Cited UNITED STATES PATENTS 3,606,812 9/l97l Riordan ..83/639 X Primary ExaminerFrank T. Yost Attorney--Ronald A. Anderson [571 ABSTRACT A hydrostatically actuated messenger type wire cutter for severing wire below the surface of a body of water consisting of a slide having an assembly for actuating a cutting tool to sever or weaken the wire at a preselected depth. A rupture disk collapses at the preselected depth, permitting water pressure to react against a piston carrying the cutting edge.

4 Claims, 2 Drawing Figures I-IYDROSTA'I'ICALLY POWERED MESSENGER STYLE WIRE CUTTER SOURCE OF THE INVENTION This invention was made in the course of, or under a contract, with the United States Atomic Energy Commission.

BACKGROUND OF THE INVENTION In a variety of oceanographic operations there is real danger of exceeding the working strengths of the wire ropes used; this is especially true in operations like coring and dredging. It is usual practice in such operations to use a weak link" at the end of the wire to connect the gear in bottom-contact. The weak link consists of a shear pin set to fail at tension corresponding to the rated working strength of the wire less the weight (in water) of the wire to be lowered. These weak links are well-calibrated, and their use has usually ensured that only gear is lost when firmly hung-up.

In some cases, however, the wire parts at or near the sheave, and in such cases it is believed that the wire above the weak link had thrown a loop around a bottom projection, such as a ledge or a boulder too large to move. Much ship time is used in maneuvering about the dredges, attempting to pull them free or to disentangle the knots protecting the weak links. Eventually the wire is winched into a zero degree wire angle and tension increased until finally the wire is parted in spite of all these efforts to avoid such a result. Tension meter records show the rated breaking strength of the wire to have been exceeded thereby indicating that the cable was never freed from its projection.

Loss of the wire in such cases is expensive, and can result in curtailed scientific programs when no replacement reel is aboard. Sometimes replacement wire has to be sent in by air, at the cost of some days delay of the ship in port, as well as the considerable freight charges.

SUMMARY OF THE INVENTION The present invention overcomes the problems mentioned above, in those situations where it is not possible to loosen a fouled wire, and when tension on the wirein excess of that rated for the weak link employed is ineffective to release the wire.

In accordance with a preferred embodiment of this inven tion, a unique wire-cutter messenger is relied upon to cut or weaken the wire rope at a location close to where fouling has taken place. The wire-cutter relies on hydrostatic pressure both to determine the depth at which it is actuated and also to provide the power to drive a cutting tool to produce the actual cutting.

It is thus a principal object of this invention to provide apparatus for the cutting of a wire close to the point of fouling.

Other objects and advantages of this invention will hereinafter become obvious from the following description of a preferred embodiment of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a preferred embodiment of this invention;

FIG. 2 is an elevation view, in partial section, of the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, wire-cutter assembly is shown mounted for use on a multi-stranded wire 12. Cutter assembly 10 would be placed (in a manner to be described later) on wire 12 when the latter becomes fouled, presumably at water bottom, by a rock or other solid object. Wire 12 would extend downwardly, at some shallow angle, from the dredging vessel (not shown) to a point on the sea bottom where the dredging or other gear is attached. Fouling would be at some point close to the dredging gear.

Cutter assembly 10 consists of a pair of spaced plates 14 and 16, separated by bars 18, 22, 24, and a bar (which is hidden) aligned with bar 24. Spacing between bars I8, 22, and 24 is such as to readily accommodate wire 12. Bars 18, 22, 24, and the hidden bar would be attached, such as by welding, to lower plate 16. Upper plate 14 is thus removable.

Cutter mechanism 26, which is cylindrical in shape, is mounted on plate 14, clamped in place by a pair of bolts, only one of which, designated 28, is shown. It will be seen that these bolts, including bolt 28, maintains the whole assembly together. 7

Referring to FIG. 2 for the details of cutter mechanism 26, it will be seen that the latter consists of a solid cylindrical body 32 with a circular axial passageway 34 of narrower diameter in the bottom portion and larger diameter in the upper portion. A cover 36 held in place by a plurality of screws 38 having an opening 42 encloses the upper surface of body 32. An O-ring '39 in a slot seals the contact between body 32 and cover 36.

Opening 42 is threaded to receive a hollow male member 44 provided with a hollow threaded cap 46. The latter when in place positions a ring 48 spanned by a rupture disk 52. Disk 52 is designed to rupture at some particular pressure which corresponds to a particular water depth. By removing cap 46 it is possible to substitute a rupture disk for any selected depth.

Passageway 34 in body 32 functions as a cylinder to accommodate a piston 54 which is stepped to fit snugly in passageway 34 as illustrated. A pair of O-rings 56 and 58 in grooves seal space 62 formed between the wall of passageway 34 and piston 54 when the latter is in its upper, retracted position (as shown). Piston 54 carries at its lower or forward end a cutting element 64 which when retracted with piston 54 as shown is free of contact with wire 12. An opening 66 in plate 14 accommodates the cutting element 64 when the latter is driven downwardly as will be described later.

In the operation of cutter assembly 10, cap 46 is removed and ring 48 is replaced with a rupture disk 52 designed to rupture at a depth slightly less than the depth of the water where the drag or other gear is located. Presumably wire 12 is fouled on sea bottom close to the gear. With plate 14 and mechanism 26 removed, assembly 10 is placed on wire 12, the parts assembled as shown, with bolts 28 holding them together. Cutter assembly 10 is then permitted to slide down wire 12 until the depth is reached where disk 52 will fail. When this occurs, water enters passageway 42 by way of male fixture 44 and urges piston 54 downwardly under great force, causing cutting element 64 to cut or damage wire 12. In the event the latter is not cut, it will be sufficiently weakened so the continued tugging will cause separation at the point where it has been weakened.

It is thus seen that there has been provided a wire cutting device which is highly useful and, because of simplicity of design, is also reliable and expendable.

What is Claimed is:

l. A hydrostatically actuated messenger type wire cutter comprising:

a. means for being mounted slidably on said wire;

b. cylinder means on the mounting means containing a piston;

c. cutting means extending from said piston in the direction of said wire; and

d. means responsive to water pressure at a preselected depth for driving said piston and cutting means into cutting contact with said wire, to at least weaken the latter.

2. The wire cutter of claim 1 in which the driving means includes a rupture disk which fails at said preselected depth of water.

3. The wire cutter of claim 2 in which said piston is actuated by said water passing through the collapsed rupture disk.

4. The wire cutter of claim 3 in which the driving means includes means for supporting said rupture disk, said supporting means being removable so as to permit use of another rupture disk designed to fail at a difierent preselected depth of water. 

1. A hydrostatically actuated messenger type wire cutter comprising: a. means for being mounted slidably on said wire; b. cylinder means on the mounting means containing a piston; c. cutting means extending from said piston in the direction of said wire; and d. means responsive to water pressure at a preselected depth for driving said piston and cutting means into cutting contact with said wire, to at least weaken the latter.
 2. The wire cutter of claim 1 in which the driving means includes a rupture disk which fails at said preselected depth of water.
 3. The wire cutter of Claim 2 in which said piston is actuated by said water passing through the collapsed rupture disk.
 4. The wire cutter of claim 3 in which the driving means includes means for supporting said rupture disk, said supporting means being removable so as to permit use of another rupture disk designed to fail at a different preselected depth of water. 